The invention relates to footwear, and particularly to athletic footwear having features which provide improved comfort to the wearer, particularly from a standpoint of modulating or controlling the temperature of the foot. The invention is primarily directed to a shoe having features to keep the foot cool and dry. Certain aspects of the invention could also be utilized in footwear designed to keep the foot warm.
Discussion of Background
The footwear industry, particularly the athletic footwear industry, has seen numerous design features introduced in order to enhance the comfort and/or performance of the wearer. Often such modifications relate to enhancing the manner in which the shoe supports the foot, such that the shoe can, for example, better absorb impacts or allow the wearer to more comfortably exert a large amount of force while reducing the possibility of injury. These designs modifications demonstrate, that comfort and performance are often interdependent. An athlete who can rely upon his or her footwear to perform without injury or discomfort can better train and perform up to their potential.
One aspect of footwear design which often receives less attention relates to foot temperature and the ability of the footwear to prevent excessive heat or, in some instances, to retain heat. For many athletic activities, such as running or tennis, the wearer must perform in hot temperatures and upon surfaces (e.g., asphalt) which can be even hotter than the ambient temperature. In these conditions, it is important for the shoe to keep the foot as cool and dry as possible. Similarly, if the athlete is to perform in cold conditions, the footwear should be able to retain heat to optimize the wearer""s performance and prevent injury.
Whether the athlete is an occasional athlete or a professional, the ability of the footwear to modulate temperature can have both comfort and performance effects. Obviously, whenever there is foot discomfort, the physical activity is less enjoyable. In addition, such discomfort can psychologically and physiologically detract from the performance of the wearer. Generally, with athletic footwear utilized, e.g., in running or tennis, it is desirable to prevent overheating of the foot. Excessive foot temperature can lead to excessive perspiration and premature fatigue (mentally and physically). Further, excessive perspiration can also detract from the wearer""s ability to react quickly, take a quick step, or change directions, since the foot is held less firmly within the shoe.
Under certain conditions, it can also be desirable to retain heat, e.g., where the athletic activity is to be performed in a cold climate. The retention of heat can be important in providing comfort to the wearer, preventing injury or frostbite, and providing better circulation. Obviously, temperature modulation is very important in enhancing the wearer""s comfort and performance.
A number of footwear designs have attempted to provide desirable temperature modulation. For example, U.S. Pat. No. 4,055,699 to Hsiung discloses the use of a four layer insole to enhance the insulating characteristics of the shoe, with the bottom layer formed of aluminized Mylar. However, the Hsiung arrangement is suitable for cold climates, but does not assist in modulating foot temperature in hot conditions. Moreover, the use of Mylar at the bottom of the insole can be problematic in that the Mylar can deteriorate or degrade with use. Further, if the Mylar is utilized in hot conditions as a bottom layer, there is an increased possibility of degradation and/or delamination of the Mylar.
Particularly from a standpoint of preventing excessive heating of the foot, the primary difficultly resides in the ability to modulate heat at the underside of the foot. However, it can be difficult to incorporate successful temperature modulating features without detracting from cushioning and support functionsxe2x80x94which are often the primary focus of athletic shoe designs in the region beneath the foot. Thus, it can be difficult to provide a design which will not interfere with the cushioning/support functions of the shoe while also providing a durable design which can keep the foot cool and dry.
It is an object of the invention to provide a shoe having enhanced capabilities in controlling or modulating the temperature of the wearer""s foot. Although the primary focus of the invention resides in the ability to prevent overheating of the foot, and to keep the foot cool and dry, certain aspects of the invention could also be advantageously utilized in retaining heat within the shoe. In a particularly preferred form of the invention a multilayer assembly, comprised of a heat resistant film disposed between two layers of strobel material, is disposed between the midsole and the insole of the shoe. The heat resistant film can be, for example, a metalized Mylar film. Such a film has a reflective surface and a non-reflective surface. Where it is desired to prevent overheating of the foot, the reflective surface of the film faces toward the midsole and acts as a barrier to reduce or inhibit the transfer of heat from hot surfaces (such as asphalt) to the foot. If desired, this arrangement could also be utilized in footwear designed to retain foot heat, in which case the reflective surface of the film would be disposed to face toward the insole. As noted above, the primary focus of the invention is upon footwear designs which can reduce overheating of the foot, to thereby keep the foot cool and dry.
With the heat resistant film disposed in the strobel material, the durability of the film is enhanced, since there is little risk of delamination, and the Mylar film is protected by the surrounding strobel material. Further, the positioning of the multilayer strobel and Mylar film layer beneath the insole is additionally advantageous in accordance with the invention, since a ventilation system is incorporated in the insole design. Thus, the multilayer strobel/Mylar assembly not only reduces the heat transfer from a hot surface to the foot, but also, the performance of the ventilation system is enhanced since the air in the ventilation system is also protected from the heat of the hot surface. Other advantageous aspects of the invention are disclosed in further detail hereinafter.